For improving the RFV level of tires, there have been proposed a manufacturing method and a tire molding machine for carrying out the method, wherein the radial force or radial runout of a product tire is measured in advance, over the entire periphery thereof, and the angle of the center axis of the bead core for a subsequently manufactured tire is controlled relative to the center axis of the carcass band. Such a technology is disclosed, for example, in the pamphlet of International Publication WO 03/045675.
This molding machine includes a pair of bead core supporting devices for holding respective bead rings which are arranged on a radially outer side of a carcass band and spaced axially from each other by a predetermined distance, and a molding drum provided with bead lock portions for radially expanding these portions of the carcass band, which are situated on the radially inner side of the bead rings, to thereby urge such carcass band portions against the bead cores, wherein at least one of the bead core supporting devices is capable of controlling the inclination angle of the center axis of the bead core held thereby.
More specifically, the above-identified patent document discloses a first embodiment of the tire molding machine that includes a molding drum having a horizontal center axis, and bead core supporting devices each comprising a base portion, a substantially vertical bead holder ring arranged on the base portion, and a bead holder ring posture control means provided for the base portion, for controlling the posture of the bead holder ring relative to the base portion. Also disclosed is a second embodiment of the tire molding machine that includes a plurality of segments, e.g., six segments, for holding the bead core, which can be independently controlled and positioned in the axial direction of the molding drum, so as to control the inclination angle of the center axis of the bead core.
However, in the case of the first embodiment of the prior art, wherein the bead holder ring posture control means is arranged on the base portion, when it is desired to modify an existing tire molding machine, which cannot control the inclination angle of the center axis of the bead core, so as to include the bead holder ring posture control means, the center axis of the bead holder ring must be necessarily situated above the center axis of the tire molding drum. It may be then necessary to carry out an extensive modification with respect to the basic structure so as to change the height of the center axis of the molding drum.
Furthermore, in the case of the second embodiment of the prior art, the plurality of segments must be each provided with a driving means for controlling the axial position, thereby making the system complex in structure, beside that when the inclination angle of the bead core is increased relative to a vertical axis, it may become difficult to accurately hold the bead cores due to steps that are likely formed between the segments.